Speedometer controllers are known that determine a vehicle speed displayed on a speedometer based on a detection signal from a vehicle speed sensor for detecting a vehicle speed based on rotation of a drive shaft transmitting engine drive force to driving wheels (Japanese Patent Application Laid-Open No. Hei. 05-162560).
In speedometer controllers of this type that use a detection signal from a vehicle speed sensor, the detection signal from the vehicle speed sensor is transmitted through a powertrain control module (hereinafter referred to as “PCM”). Hence, in the event of failure of the PCM or the like, a problem that displaying speeds is impossible arises because a signal corresponding to a vehicle speed obtained based on the detection signal from the vehicle speed sensor is not transmitted to the speedometer.